/**
 * Copyright 2012 Twitter, Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package rfx.server.util.ua;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Operating System parser using ua-parser. Extracts OS information from user
 * agent strings.
 * 
 * @author Steve Jiang (@sjiang) <gh at iamsteve com>
 */
public class OSParser {
	
	
	private final List<OSPattern> patterns;

	public OSParser(List<OSPattern> patterns) {
		this.patterns = patterns;
	}

	public static OSParser fromList(List<Map> configList) {
		List<OSPattern> configPatterns = new ArrayList<OSPattern>();

		for (Map<String, String> configMap : configList) {
			configPatterns.add(OSParser.patternFromMap(configMap));
		}
		return new OSParser(configPatterns);
	}

	public OS parse(String agentString) {
		OS os;
		for (OSPattern p : patterns) {
			if ((os = p.match(agentString)) != null) {							
				return os;
			}
		}
		return new OS("Other", null, null, null, null);
	}
	
	public List<OSPattern> getPatterns() {
		return patterns;
	}

	protected static OSPattern patternFromMap(Map<String, String> configMap) {
		String regex = configMap.get("regex");
		if (regex == null) {
			throw new IllegalArgumentException("OS is missing regex");
		}

		return (new OSPattern(Pattern.compile(regex),
				configMap.get("os_replacement"),
				configMap.get("os_v1_replacement"),
				configMap.get("os_v2_replacement")));
	}

	protected static class OSPattern {
		private final Pattern pattern;
		private final String osReplacement, v1Replacement, v2Replacement;

		public OSPattern(Pattern pattern, String osReplacement,
				String v1Replacement, String v2Replacement) {
			this.pattern = pattern;
			this.osReplacement = osReplacement;
			this.v1Replacement = v1Replacement;
			this.v2Replacement = v2Replacement;
		}
		

		public String getOsReplacement() {
			return osReplacement;
		}


		public String getV1Replacement() {
			return v1Replacement;
		}


		public String getV2Replacement() {
			return v2Replacement;
		}


		public OS match(String agentString) {
			String family = null, v1 = null, v2 = null, v3 = null, v4 = null;
			Matcher matcher = pattern.matcher(agentString);

			if (!matcher.find()) {
				return null;
			}

			int groupCount = matcher.groupCount();

			if (osReplacement != null) {
				family = osReplacement;
			} else if (groupCount >= 1) {
				family = matcher.group(1);
			}

			if (v1Replacement != null) {
				v1 = v1Replacement;
			} else if (groupCount >= 2) {
				v1 = matcher.group(2);
				if (v2Replacement != null) {
					v2 = v2Replacement;
				} else if (groupCount >= 3) {
					v2 = matcher.group(3);
					if (groupCount >= 4) {
						v3 = matcher.group(4);
						if (groupCount >= 5) {
							v4 = matcher.group(5);
						}
					}
				}
			}
			return family == null ? null : new OS(family, v1, v2, v3, v4);
		}
	}
}